I've finally written up my guide to recording real-time gameplay in RetroPie’s RetroArch emulators; this approach requires no external hardware, and allows 60fps capture in emulators from the VCS to PlayStation.

@meleu there's no reason it wouldn't work, but some of the more demanding emulators may struggle to run at full speed whilst recording - that said, the ffmpeg config can be tuned so it may well be possible to trade quality for more speed

I would like to suggest an improvement to avoid that inconvenience of rename the file before launch RetroArch again. I was thinking to name the files with an appending timestamp. Example: recording_VCS_2016-07-14-221955.mkv(year-month-day-hourminutesecond). To achieve it you just have to change the --record option to something like this:

@meleu No time like the present; I've updated the 'Naming the Recording File' boxout with the following:

UPDATE: RetroPie forum member meleu suggested an improvement to avoid the inconvenience of renaming the file before each emulator launch, by automatically appending the filename with a timestamp (year-month-day-hourminutesecond), for example:recording_VCS_2016-07-14-221955.mkv
This is achieved by updating the --record parameter as follows:--record /media/pi/EXT_HDD/RPi_AVI/recording_VCS_$(date +%Y-%m-%d-%H%M%S).mkv

Anyone else having issues getting this done?
I've recompiled FFMpeg along with the extra codecs, even downloaded and ran the script in the same site.
RetroArch compiles fine, even though FFMPeg is present, and the --disable-ffmpeg part is removed,
I still don't have the Recording option (Done this 3-4 times now)

@LSolrac2 have you tested ffmpeg by transcoding some video files from the command line, to ensure it has correctly built and installed?
Has ffmpeg been installed to the default location so that it can be found by other applications (can you type ffmpeg from anywhere / directory at the terminal)?

@LSolrac2 it's worth asking, although I'm sure you'll have followed the process in order, but has Retroarch been recompiled after ffmpeg has been built and installed?
[Edit] re-reading your post, it seems that you did install ffmpeg before recompiling retroarch, so this question is moot.

@LSolrac2 hi, some further questions (there are so many parts involved in a RetroPie system...)

Is your installation from Raspbian image, with RetroPie installed on top, or from a RetroPie image?

If you used a RetroPie image, do you have the lxde / Raspbian desktop?

In either case, which version of Raspbian Linux is installed (Wheezy or Jessie)?

Which version of Retroarch is installed on your system? This is shown at the bottom of the window when the Retroarch GUI menu is being accessed? My version is 1.3.4 on RetroPie 3.8. I notice in retropie's github that the retroarch framework was updated on 17th June, just after I last ran through the installation process . at a glance i can't tell from the source if anything has changed that could be causing the issue.

Part way through the ffmpeg compilation at the moment, having installed RetroPie.

I have noticed that RetroArch is now version 1.3.6, released June 17th 2016 (my 3.8 RetroPie installation has 1.3.4, which was the released in May 2016), although there's nothing in the release notes to suggest a problem with ffmpeg recording.

I've checked RetroPie's RetroArch setup script, and this seems to be as it was previously, including the original --disable-ffmpeg parameter.